Table 2.
Comparison of secondary attack rate during COVID-19 outbreaks in two Chinese restaurants before and after enhancement of indoor air dilution.
| Outbreak R1 | Outbreak R2 | P value | |
|---|---|---|---|
| Customers | |||
| Number of exposed | 76 | 207 | |
| Number of secondary infected | 22 | 7a | |
| Secondary attack rate | 28.9% | 3.4% | P<0.001 |
| Restaurant staff | |||
| Number of exposed | 19 | 22 | |
| Number of secondary infected | 10 | 0 | |
| Secondary attack rate | 52.6% | 0% | P<0.001 |
| Secondary attack rate (overall) | 33.7% | 2.6% | P<0.001 |
Note. Outbreak R1 occurred on 19th February 2021 (before enhancement of indoor air dilution). Outbreak R2 occurred on 27th December 2021 (after enhancement of indoor air dilution).
a
Excluding the index case (case 1), there were 7 secondary infected cases in this outbreak.